Reconstructing Earth's History

Roughly how old is the Earth?

• hundreds of years old

• thousands of years old

• millions of years old

• billions of years old

When certain fossils appear in one rock strata but disappear in the next one, what probably happened?

• mass extinction

• the organisms moved

• the organisms evolved very quickly

• the environment was no longer prone to creating fossils

Mass extinctions are used to mark the end of one __________ and the beginning of another.

• year

• rock strata

• human era

• geologic time span

Which of the following is the shortest unit of time?

• eon

• era

• period

• epoch

What era do we live in?

• Cenozoic

• Mesozoic

• Paleozoic

• Precambrian time

Why do we have so much information about the current eon (Phanoerozoic) even though it only represents about 10% of the Earth’s lifespan?

• Weathering was much worse before this eon.

• There aren’t many rocks left from previous eons.

• The Earth didn’t have a crust before the Phanoerozoic.

• Most of the Earth’s crust was formed during this epoch.

Scientists mostly agree that the solar system formed in accordance with the _________

• star theory

• big bang theory

• nebular hypothesis

• black hole hypothesis

Because meteorites formed __________, they are good direct evidence to determine the age of the Earth.

• after the Earth

• before the Earth

• at the same time as the Earth

• very recently in geologic time

During the formation of the Earth, _________ elements like iron fell to the core and ___________ elements rose toward the surface.

• light; heavy

• heavy; light

• radioactive; stable

• stable; radioactive

What does the Iron Catastrophe refer to?

• the iron shortage of the 1940s

• the formation of Earth’s iron core

• the disruption of rock strata by iron ore

• the impact of the Canyon Diablo meteorite